Private/professional radios, such as mobile radios, portable radios, and the like, may be configured to communicate (send information to and receive information from) with each other in direct mode or in repeater mode. In direct mode, radios communicate directly with one another. In repeater mode, radios communicate with one another through a repeater, wherein information is sent from a transmitting radio through the repeater to one or more receiving radios. Radios may also communicate through a dispatcher (dispatch center) that may be connected directly to a repeater via a wireline link or that may be connected to a control station (a mobile radio mounted to a desk or a rack) via a wireline link. Dispatchers are typically stationary. Each radio in communication with another radio and/or the dispatcher, either in direct mode or repeater mode, may need to be configured to alert its user when it is out of communication range from the other radio(s) with which it was previously able to communicate, or when it is out of communication range from the dispatcher. The dispatcher also may need to know when a radio is out of communication range. Accordingly, each radio that communicates with other radios through a dispatcher has to keep track of the dispatcher; the dispatcher has to keep track of each radio for which it facilitates communications; and each radio in direct communications with other radios needs to track the other radios in its direct communications range.
The following examples provide scenarios of when a radio in communication with other radios and/or the dispatcher, either in direct mode or repeater mode, needs to alert its user when it is out of communication range from the other radios and/or the dispatcher with which it was previously able to communicate. Consider an example where, as a security precaution, radios used by drivers in a fleet of armored trucks need to be in communication with each other and/or with a dispatcher at all times, either in direct mode or repeater mode. Should an incident occur that would place a first radio out of the communication range of one or more radios in the fleet of armored trucks and/or dispatcher, the dispatcher and/or the users of the other radio(s) need to be notified that the first radio has moved out of communication range. Additionally or alternatively, the first radio may need to alert its user that the first radio can no longer communicate with one or more radios in the group. In another example, to make it easier and more efficient for remote workers to remain in hassle-free contact with other remote workers, radios used by each remote worker may be configured to remain in contact with a base operation. Thus, each radio in such a configuration may be set up to notify its user when the radio moves out of communication range from the base operation. In another example, a group can be configured so that a leader can determine the status of group members by monitoring when radios used by group members move out of the leader radio's communication range.
In a conventional Auto-Range Transpond System (ARTS), when a group of radios are configured to directly communicate with each other or when the group of radios are configured to communicate through a dispatcher, each radio periodically transmits an unconfirmed “beacon” to the other radios in the group or to the dispatcher. An unconfirmed beacon is a one-way transmission with no feedback provided to the sending radio as to whether the entire message is received without uncorrectable errors. The beacon is a push-to-talk identifier associated with a transmitting radio that announces the transmitting radio's presence to other radio(s) and/or the dispatcher within the transmitting radio's communication range. Just because a receiving radio is able to receive a signal from a transmitting radio, this does not imply that the receiving radio is able to transmit information to the transmitting radio. Consider the following example where a portable radio with a lower transmitter power is able to receive a beacon sent from a mobile radio with a higher transmitter power. Radios with lower transmitter power typically have a transmit range that is more limited than the transmit range of radios with higher transmitter power. Therefore, if a radio with a lower transmitter power, in this case the portable radio, can receive a signal from a radio with a higher transmitter power, in this example the mobile radio, this does not imply that the portable radio with the lower transmitter power is also able to send information to the mobile radio with the higher transmitter power. Because the transmitted beacon is unconfirmed and no response is required or provided in ARTS, even when the portable radio can only receive information from the mobile radio, but cannot send information to the mobile radio because of the portable radio's lower transmitter power, the mobile radio and the portable radio may erroneously determine their communication status with respect to each other. The portable radio may correctly conclude that it is capable of receiving from the mobile radio, but may incorrectly conclude that it is capable of transmitting to the mobile radio. Conversely, the mobile radio may correctly conclude that it is not capable of receiving from the portable radio, but may incorrectly conclude that it is not capable of transmitting to the portable radio.
In addition, ARTS does not provide an avenue for a radio to proactively provide a bi-directional communication range status information of other radios and/or the dispatcher. ARTS also does not provide an avenue for a radio to alert its user when it can no longer transmit information to another radio before the user presses a switch, such as a push-to-talk button.
Furthermore, ARTS only operates in analog mode. Radios may operate in different modes, for example, analog or digital mode; direct, talkaround, or repeater mode; conventional or trunked mode. Accordingly, each radio needs to support different modes of operation. Although radios currently operating in trunked systems and multi-site systems may provide an “out-of-range” (OOR) indication to users to indicate that the radio is unable to receive information from a system infrastructure, the OOR indication does not provide an indication that a target radio is within communication range, does not provide a proactive indication when the radio is unable to transmit into the system, and the OOR indication is not present in direct/talkaround or single site conventional operating modes.
In one implementation, ARTS radios can transmit their beacons as frequently as every twenty (25) seconds and an ARTS beacon transmission is approximately five hundred (500) milliseconds (msec) in duration. Assuming that transmissions are perfectly scheduled for maximum utilization of a channel, this would imply that ARTS is capable of supporting approximately fifty (50) radios on an access channel. However, due to the random access nature of the channel on which radios transmit their beacons, transmissions are not typically perfectly scheduled. Therefore, ARTS is typically capable of supporting about ten (10) to fifteen (15) radios at a time. A system capable of supporting more radios is desirable.
Some radios currently include a user-initiated radio check feature that operates in a one-to-one mode, wherein a first radio queries a second radio to determine the second radio's presence. When the first radio receives a response to a query sent to the second radio, the first radio can conclude that its query was successfully transmitted to the second radio because the second radio's response was successfully received (bi-directional capability). The radio check feature therefore allows the first radio to check for bi-directional connectivity with the second radio. In other words, the radio check feature allows the first radio to determine that it can both transmit information to and receive information from the second radio. The radio check feature in conjunction with a provisioned list of radios could be modified to operate periodically and automatically. However, a single radio check transaction (between a pair of radios) on, for example, an European Telecommunications Standards Institute-Digital Mobile Radio (ETSI-DMR) channel consumes approximately six hundred (600) msec of time on the channel. The 600 msec may include, for example, channel access rules (approximately 180 msec), battery saver preambles (approximately 120 msec), the radio check control block signaling (CSBK) (approximately 60 msec), a delay through a repeater (approximately 60 msec), processing latency in the target radio (approximately 60 msec), a response from the target radio (approximately 60 msec), and another delay through the repeater (approximately 60 msec). Because radio check is fundamentally a one-to-one feature, as the number of radios in a system grows, the number of radio check operations performed in the system can be expected to grow exponentially. A high number of radio check operations may degrade the random access channels on which radios transmit their signal. Random access channel degradation and the likely forced spacing required between messages on a random access channel so that the channel can also transmit actual payload data may limit the number of radio check operations performed on the system.
In cases where radios communicate with each other and/or a dispatcher through a repeater, some radios currently include a channel access feature that permits a high speed handshake (e.g., request and grant) between a radio and the intermediary repeater. When setting up a group call, there is typically one transmitter radio and multiple receiver radios. If each receiver radio provided a response to the high speed handshake, this would result in chaos on the channel with the multiple responses possibly colliding with one another and would be inefficient. Having a repeater, when present, provide the response to the transmitting radio is more efficient. The high speed handshake between the transmitting radio and the repeater, therefore, mitigates any channel access collisions as well as confirms that the transmitting radio has in fact accessed the repeater before it commences with a voice or data transmission. Because this feature only allows handshakes with the repeater, not target radio(s), there is no confirmation of end-to-end connectivity between the transmitting radio and the target radio(s), prior to the transmitting radio starting a call. In addition, because the high speed handshake is only with the repeater, this approach cannot be used in a direct/talkaround mode. Furthermore, this feature provides information reactively, not proactively, i.e., the transmitting radio does not know any communication range status until a call is attempted.
Accordingly, there is a need for a method and apparatus for automatically and proactively determining the communication range status of communicating radios.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.